1. Field
The presently disclosed subject matter relates to semiconductor light-emitting devices in which light emitted from at least one semiconductor light-emitting chip is wavelength-converted by a wavelength converting layer, and to manufacturing methods for the same. More particularly, the disclosed subject matter relates to semiconductor light-emitting devices for a vehicle light and the like, which can emit light having a high light-emitting efficiency from various small light-emitting surfaces, and to methods of manufacturing such devices.
2. Description of the Related Art
Semiconductor light-emitting devices, in which a part of light emitted from a semiconductor light-emitting chip is converted into light having a different wavelength by a phosphor and in which a mixture light including the light having the different wavelength mixed with the light emitted directly from the light-emitting chip is emitted, have been used as a light source for various lighting units. Conventional semiconductor light-emitting devices including a wavelength converting material, for example, are disclosed in Patent Document No. 1 (Japanese Patent Application Laid Open JP2004-31989).
FIGS. 11a and 11b are side cross-sectional views showing a conventional lead frame type light-emitting device and a conventional radial type light-emitting device, respectively, which are disclosed in Patent Document No. 1. The conventional lead frame type light-emitting device 20 includes: a casing 26 having a cavity 27; a pair of lead frames 22, 23 located on a bottom surface of the cavity 27 of the casing 26; a semiconductor light-emitting chip 21 having a bottom electrode and a top electrode mounted on the lead frame 22, the bottom electrode electrically connected to the lead frame 22, and the top electrode electrically connected to the lead frame 23 via a bonding wire 24; and a phosphor resin 25 located on an opening of the cavity 27 of the casing 26 so as to be able to wavelength-convert light emitted from the semiconductor light-emitting chip 21.
The conventional radial type light-emitting device 30 includes: a casing 36 composed a transparent resin; a pair of lead frames 32, 33 located in the casing 36; a semiconductor light-emitting chip 31 having a first electrode and a second electrode mounted in a cup of the lead frame 32, the first electrode electrically connected to the lead frame 32 via a bonding wire 34a, and the second electrode electrically connected to the lead frame 33 via a bonding wire 34b; a phosphor resin 35 disposed in the cup of the lead frame 32 so as to encapsulate the semiconductor light-emitting chip 31.
The lead frame type light-emitting device 20 may emit a wavelength-converted light via the phosphor resin 25 so as to expand the light from the cavity 27 of the casing 26. Accordingly, it may be difficult for the lead frame type light-emitting device 20 to reduce the size of a light-emitting surface because the light expands from the cavity 27. Additionally, the radial type light-emitting device 30 may emit a wavelength-converted light in a radial fashion from the casing 36, and therefore may also be difficult to reduce the size of a light-emitting surface.
In addition, conventional lead frame type semiconductor light-emitting devices that may emit a wavelength-converted light having a high brightness are disclosed in Patent Document No. 2 (Japanese Patent Application Laid Open JP2004-40099) and Patent Document No. 3 (Japanese Patent Application Laid Open JP2008-507850). A light-emitting device disclosed in Patent Document No. 2 includes a concave reflective material in a cavity that mounts semiconductor light-emitting chips therein so that light emitted from the semiconductor light-emitting chips is efficiently emitted from the cavity.
Another light-emitting device disclosed in Patent Document No. 3 includes a plurality of semiconductor light-emitting chips and a cavity, which mounts the plurality of light-emitting chips at a predetermined interval therein. Thereby, Patent Document No. 3 discloses that semiconductor light-emitting devices may emit a wavelength-converted light having a high brightness from the cavity such that the device may be used as a light source for a vehicle headlight.
However, when the semiconductor light-emitting devices are used as a light source for a lighting unit such as a vehicle headlight, which controls light emitted from the light-emitting devices using a reflector and/or a projector lens, a light-emitting device having a small light-emitting surface may be desired to efficiently control light emitted from the light-emitting device with a small optical structure. Therefore, the semiconductor light-emitting devices including the cavities disclosed in Patent Documents No. 1 to No. 3 may not be a match for the above-described usage.
A semiconductor light-emitting device having a small light-emitting surface can be used as a light source for a vehicle headlight using a projector lens and is disclosed in Patent Document No. 4 (Japanese Patent Application Laid Open JP2009-218274). FIG. 12 is a cross-sectional view showing the conventional semiconductor light-emitting device disclosed in Patent Document No. 4.
The conventional semiconductor light-emitting device 40 includes: a base board 42; semiconductor light-emitting chips 41 mounted on the base board 42; a wavelength converting layer 45 disposed on the semiconductor light-emitting chips 41; and a reflecting member 46 located around the semiconductor light-emitting chips 41 and the wavelength converting layer 45 so as to encapsulate the semiconductor light-emitting chips 41 along with the base board 42 and the wavelength converting layer 45.
The conventional semiconductor light-emitting device 40 can emit a wavelength-converted light from a small light-emitting surface via the wavelength converting layer 45, because the light-emitting surface of the conventional semiconductor light-emitting device 40 can become nearly equal to top surfaces of the semiconductor light-emitting chips 41. In addition, because light emitted from side surfaces of the semiconductor light-emitting chips 41 and the wavelength converting layer 45 may be reflected into the semiconductor light-emitting chips 41 and the wavelength converting layer 45 by the reflecting member 46 and may be emitted from a top surface of the wavelength converting layer 45, a light intensity in a frontward direction of the conventional light-emitting device 40 may improve.
However, when a side surface of the reflecting member 46 is located perpendicular to the base board 42 mounting the semiconductor light-emitting chips 41 in the semiconductor light-emitting device 40 as shown in FIG. 12, light reflected on the side surface of the reflecting member 46, which contacts with the side surfaces of the semiconductor light-emitting chips 41, may return into the semiconductor light-emitting chips 41. Accordingly, because an absorbing band of the semiconductor light-emitting chips 41 includes a wavelength of the reflected light, the reflected light and an absorbing light may increase in the semiconductor light-emitting chips 41. The increase of the reflected light and the absorbing light may cause a decrease in a total amount of light flux emitted from the conventional semiconductor light-emitting device 40.
Therefore, semiconductor light-emitting devices that can emit a wavelength-converted light having a high light-emitting efficiency from a small light-emitting surface have been developed by inventors of the presently disclosed subject matter.
The above-referenced Patent Documents are listed below, and are hereby incorporated with their English abstracts in their entireties.    1. Patent Document No. 1: Japanese Patent Application Laid Open JP2004-31989    2. Patent Document No. 2: Japanese Patent Application Laid Open JP2004-40099    3. Patent Document No. 3: Japanese Patent Application Laid Open JP2008-507850    4. Patent Document No. 4: Japanese Patent Application Laid Open JP2009-218274    5. Patent Document No. 5: Japanese Patent Application No. 2010-137365    6. Patent Document No. 6: Japanese Patent Application No. 2010-173852    7. Patent Document No. 7: Japanese Patent Application No. 2010-201985
The disclosed subject matter has been devised to consider the above and other problems, features, and characteristics. Thus, embodiments of the disclosed subject matter can include semiconductor light-emitting devices that can emit a wavelength-converted light having a high light-emitting efficiency from various small light-emitting surfaces, and associated manufacturing methods that do not cause and/or are designed to prevent some of the above-described problems, concerns, and characteristics related to a wavelength converting layer. The disclosed subject matter can also include a semiconductor light-emitting device using a plurality of semiconductor light-emitting chips, which can be used for wavelength-converting light having a high light-emitting efficiency from various small light-emitting surfaces, and which can also improve color variability between light emitted from the light-emitting chips.